CrCN/CrN+ta-C multilayer coating for applications in wood processing

The paper presents mechanical and tribological properties of CrCN/CrN and CrCN/CrN+ta-C multilayer coatings. Tetrahedral carbon (ta-C) layer formed using the pulse cathodic arc evaporation method are characterised by high hardness –45 GPa, very low friction coefficient—below 0.1 and a low wear rate −1.3×10−17 m3N−1 m−1 providing promising application perspectives.Three sets of tools—planer knives for cutterheads were tested: uncoated (as reference), tools with a CrCN/CrN coating and tools with CrCN/CrN coating with additional friction-reducing tetrahedral carbon (ta-C) layer. The results of investigations indicate that the “tool life” depends on the type of coating and machining conditions. The blades covered with CrCN/CrN multilayer coating after machining of dry, seasoned pine timber showed a twofold increase of durability, and knives covered with CrCN/CrN+ta-C multilayer coating were characterised further by about 15% higher durability. Durability of knives tested in the course of rounding of wet pine timber, despite relatively high depth of machining was improved and for cutters with a CrCN/CrN coating increased more than twice, while the use of the additional ta-C layer on the multilayer coating improved durability by almost 5 times.

► CrCN/CrN multilayer coating shows high hardness and very good adhesion.
► ta-C top layer shows excellent mechanical and tribological properties.
► The lowest wear of the cutting edge shows CrCN/CrN+ta-C coating.
► The multilayer coatings increase the durability of tools for woodworking.